Size:L neck 16-28cm, mouth 18-30cm; XL neck 20-30cm, mouth 23-34cm, XXL neck 22-35cm, mouth 28-38cm. Humane way to prevent biting and unwanted chewing This muzzle is great for restraining your dog's ability to bite, chew and bark while still allowing your dog to breathe, pant, and drink water. Bonus collar and connection strap holds muzzle in place Fit connection makes it a snap to keep your best buddys muzzle securely in place, even for the rowdy pups Easily connect it to your dogs collar or use the included bonus collar for added support. Quality sliders for a perfect fit No cheap plastic buckles for adjusting the fit here The muzzle uses high-quality sliders for adjustments that wont loosen over time, ensuring a comfortable fit for any dog. Any excess strap length can easily be secured with a hook and loop fastener to prevent loose ends as well.